Download STEPS OF THE SCIENTIFIC METHOD

STEPS OF THE SCIENTIFIC METHOD
1. Observation of situation that leads to a question: How does this occur, and why? What would
happen if ____ was removed or added? What information do we already know about this
situation?
2. Hypothesis formation (one-sentence prediction): A plausible reason why this occurs is
______. If _____ was removed or added, __________ will happen.
3. Design an experiment that produces data to collect. Data is FACTUAL information that is
gathered. The experiment must be described in such detail that anyone else can read your
notes and repeat the experiment exactly. The set up, equipment, and step-by-step procedure
must all be this detailed. You must identify all possible variables and eliminate all but the
one you want to test. The same experiment must be repeated with a CONTROLLED
situation, in which no variables are tested. A control subject or group must go through all the
steps of the experiment except it is not exposed the factor being tested. For example, if your
hypothesis is that a particular bug will prefer sugar water to regular water, and you put the
sugar water on the right side of a plate and the regular water on the left side of the plate and
count the number of times the bug turns to the right, you must repeat the experiment with the
same plate but with plain water on both sides of the plate. If the new bug turns more often to
the right, it might be that the surface of the plate has an irregularity that the bug finds
undesirable, and that it has nothing to do with the water content.
4. Analysis of the data: Usually a table is used to record the data, and the data is later plotted on
a graph to show trends or relationships within the data. Do not draw conclusions at this
phase.
5. Make a conclusion: Explain what the data means to you. Describe any problems with the
experiment and list all the possible reasons why there might be errors in your experiment.
Suggest improvements that could be made if you were to repeat this experiment in the future.
Lastly, state whether your data supported your hypothesis or not, or whether it was
inconclusive. Remember, experimental data can support, but DOES NOT PROVE your
hypothesis.
POSSIBLE FAULTS IN STUDIES
A.
B.
C.
D.
E.
F.
Conclusion is not supported by experimental evidence
Biased sampling
Inadequate controls
Inappropriate extrapolation of the experimental group to the general population
Sample size is too small
Other problems not listed
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EXPERIMENT FROM OBSERVATION
1. OBSERVATION
Have you observed that tall people have big hands and big feet? But do most tall people have big
hands and small people have small feet?
2. HYPOTHESIS
Tall people will have big hands and big feet, and small people will have small hands and small
feet.
3. EXPERIMENTAL PROCEDURE
Everyone in the class will record their height, shoe size, and the distance between the tip of their
pinky and the tip of their thumb. All of this data will be collected on the following table:
NAME HEIGHT SHOE SIZE HAND WIDTH
4. DATA ANALYSIS
Make two graphs. On the first graph, plot the height on the y axis, and the shoe size on the x
axis. On the second graph, plot the height on the y axis and the hand width on the x axis. Note
whether there is a linear trend on the points of the graph that lead upward in shoe/hand size as
height increases.
5. CONCLUSION
Was there a direct relationship between the two traits on the first graph?
Was there a direct relationship between the two traits on the second graph?
Was there anyone in the class that did not fit the trend?
How do you interpret this data?
Does the data support your hypothesis?
Can you make generalizations from the entire human population from this experiment? Why?
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Scientific Literacy
Scientific literacy means more than being able to design and conduct experiments. You must also be
able to understand how scientific research affects your life and your decisions. Consider each of
these mini-cases and indicate what you think should be done in each situation. Be prepared to share
your answers with your classmates.
1. A researcher working for an herbal medicine company conducts an experiment on 10 middle-aged
men. He tells them that he is testing an herbal medication that scientists think will make people feel
more energetic. He instructs them to take one herbal medicine tablet a day for one week. After a
week he asks them if they feel more energetic. He reports that 9 out of 10 people feel more energetic
after taking the medication. Would you buy this medication? Explain why or why not.
2. A college professor noticed that the men and women in her class usually formed male-only or
femaleonly groups. She wondered if pheromones would encourage gender mixed groups. Without
explaining what she was doing, she asked the women in the class if they would like to try a free
sample of a new perfume. She did not tell them that the perfume contained a pheromone that
attracted members of the opposite sex. Do you think this is appropriate? Explain why or why not.
3. Scientists have discovered a medicine that they feel has the potential to cure a deadly form of
childhood cancer. They need to test the medicine to be sure that it is safe and effective. Should they
test this medicine on animals before they begin tests on humans? Explain why or why not.
4. Parkinson's disease is a progressive neurological disease that gradually destroys a person's control
of voluntary movements. Scientists have tested a treatment for Parkinson's disease in monkeys who
showed disease symptoms. They drilled holes in the skulls of two randomly selected groups of
monkeys. The experimental group had fetal tissue injected into their brains. The control group had
distilled water injected into their brains. The treatment was 80% effective in treating the symptoms
of the disease in monkeys. You have recently been diagnosed as having Parkinson's disease.
Researchers have asked you to participate in their clinical trials to test the fetal tissue transplant
treatment. Would you agree to become a subject in these clinical trials? Explain why or why not.
5. Scientists are conducting a long-term (3-year) double-blind placebo-controlled clinical trial on a
chemotherapy they hope will cure prostate cancer. They want to determine if the chemotherapy is
safe and effective. They randomly assign patients to be members of the experimental or control
group. After six months they found that early treatment with the chemotherapy results in a 90% cure
rate with no dangerous side effects. Should they offer the medicine to people in the control group
now or continue the research as planned? Explain why or why not.
6. Testing and FDA approval are not required for natural herbal medications such as Ginkgo biloba,
St. John's wort, and ginseng. Do you think people should use medicines that don't have FDA
approval? Explain why or why not.
7. During World War II, unethical scientists did research on the effects of radiation on humans. They
used people in concentration camps as their experimental group--exposing them to dangerous does
of radiation. The results of these experiments have recently been discovered. Should this information
be released? Explain why or why not.
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Analyzing the Scientific Method: Case Studies
Many of the decisions about the foods we eat, the medicines we take, and the activities we
participate in are based, in part, upon health information. Some of this information comes from
well-executed studies that adhere to the scientific method, but some comes from flawed
investigations. For the following real-life examples, decide whether or not the scientific method
was followed. If it was not, indicate which of the following specific faults (A-F) was present and
fully explain your reasoning.
Possible Fault in Study:
A. Conclusions not supported by experimental evidence
B. Biased sampling
C. Inadequate controls
D. Inappropriate extrapolation of the experimental group to the general population
E. Sample size too small
F. Other problem besides the ones listed in A-E.
Case # One: Running during Pregnancy
"I ran 4 miles (approximately 6 kilometers) every morning when I was pregnant with my first
child," the woman told her physician, "and Jamie weighed only 3 pounds (approximately I
kilogram) at birth. This time, 1 didn't exercise at all, and Jamie's sister weighed 8 pounds
(approximately 3 kilograms). Therefore, running during pregnancy must cause low birth weight".
Your Interpretation:
Case #Two : Oat Bran and Cholesterol
500 Caucasian men who had hypercholesterolemia, with blood cholesterol levels between 300
and 400, were selected for a clinical study. All of the men were between ages 30-50, and worked
white-collar jobs in the Midwestern states. Half of the group were given a standard diet which
included 5 cups of oat bran daily. Half of the group were given a standard diet plan with no oat
bran. All of the men had blood cholesterol levels tested by objective hospitals at the beginning
and end of the study. After two months, the group who had eaten oat bran had a 20% decrease in
their cholesterol levels. The group who had not eaten any oat bran had no change in cholesterol
levels. The cereal company conducting the study concluded that if all people ate oat bran daily,
their cholesterol levels would decrease. (And immediately started to advertise that!)
Your Interpretation:
Case #Three : Toxics at Love Canal
A dumping site in the small town of Love Canal, New York, was used for the disposal of
industrial chemical wastes from 1970-1975. In 1980, the housing inspector noticed traces of
toxic substances in the basement walls of the local schools and homes. The local hospital noticed
that there were 25% higher numbers of birth defects during 1970-1980. The hospital then offered
free genetic tests and found that 20% of the adult volunteers/residents of Love Canal contained
genetic abnormalities. The exposure to those industrial chemical wastes must have been the
cause the genetic abnormalities and higher birth defect incidence.
Your Interpretation:
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Case #Four: Vasectomy
Each year, 500,000 American males join the 10 million who have already had a vasectomy, a
simple sterilization procedure. In the early 1970's, animal studies suggested that heart disease
might be a complication of vasectomy. To test this hypothesis, a study involving more than
20,000 men was begun. In this study, each of 10,000 vasectomized men was paired with a
nonvasectomized man of the same age, race and marital status and living in the same
neighborhood at the time of the surgery. Each man was extensively questioned about medical
conditions (including 54 conditions statistically most likely to be associated with vasectomy) and
health and life-style habits, such as smoking, drinking, diet, exercise, and frequency of checkups.
Medical records were carefully evaluated. The results of this study showed that vasectomized
men had no significantly higher rates from any of the health conditions examined. Conclusion:
vasectomy is safe.
Your Interpretation:
Case #Five : Cancer Researcher
A former National Cancer Institute (NCI) researcher was bothered by the practice of turning
down large number of cancer patients who wanted to participate in clinical trials. His solution
was to leave the institute and start his own company, which offers to do research on individuals'
tumors. This research could lead to personalized experimental treatments. However, this
researcher's company is not supported by government funds, so patients have to pay for the
research service - about $60,000 a year. The company publishes the results of its research.
Your Interpretation
Case #Six : Cancer Trials
The National Cancer Institute (NCI) sponsors clinical trials at its Maryland headquarters and in
several research hospitals around the country. New treatments are carried out on human cancer
patients and the results evaluated. Standard cancer treatments are used as controls. There are
many more cancer patients seeking to participate in these trials than there are spaces available for
them. The policy of the NCI is to select the healthiest, strongest patients possible - what one
cancer researcher calls "the perfect patient", The goal is to give the new treatment the maximum
chance of working by testing it on a patient who has cancer but is otherwise young, strong, and
healthy. Whenever results of such trials seem promising, television new shows excitedly
announce them as "breakthroughs".
Your Interpretation:
Case #Seven : Pyruvate & Weight Loss
A study conducted at the U. Pittsburgh School of Medicine found that obese women who were
given pyruvate supplements for three weeks lost an average of 13 pounds weight (of which 8.8
pounds was fatty tissue). The tested women had an average weight of 244 pounds. During the
study, the subjects were on a liquid diet consisting of 1000 calories per day and were ingesting
30 grams of pyruvate daily. The control group consumed an equal amount of carbohydrates
(instead of pyruvate). One health and nutrition store wants to start selling pyruvate as "a
phenomenal weight-loss pill for overweight women".
Your Interpretation:
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